Reduced Gd-EOB-DTPA uptake might be an early event of hepatocarcinogenesis, preceding portal blood flow reduction. The hepatobiliary phase of Gd-EOB-DTPA-enhanced MRI may help estimate histological grading, although difficulties exist in differentiating HCCs from DNs.

Hyperintensity on T2-weighted images is an independent and strong risk factor at baseline for subsequent hypervascularization in hypovascular nodules in patients with chronic liver disease. Tumor volume doubling time of less than 542 days was associated with a high rate of subsequent hypervascularization.

Some HCC were assessed as incomplete ablation on the CT fusion images, although considered completely ablated on side-by-side images at the time of treatment, and incomplete ablation was revealed to be the only independent risk factor for LTP. The CT fusion imaging enables quantitative and accurate evaluation of treatment effect of RFA.

In stepwise hepatocarcinogenesis, uptake of Sonazoid starts decreasing later than that of Gd-EOB-DTPA. Although signal reductions on the post-vascular phase of SEUS or hepatobiliary phase of Gd-EOB-DTPA-enhanced MRI suggest HCC, hypoechoic appearance on the post-vascular phase of SEUS might be HCC-specific, particularly progressed HCC.

Background and Aims: Extracted-overlay fusion imaging is a novel computed tomography/magnetic resonance-ultrasonography (CT/MR-US) imaging technique in which a target tumor with a virtual ablative margin is extracted from CT/MR volume data and synchronously overlaid on US images. We investigated the applicability of the technique to intraoperative evaluation of radiofrequency ablation (RFA) for hepatocellular carcinoma (HCC). Methods: This retrospective study analyzed 85 HCCs treated with RFA using extracted-overlay fusion imaging for guidance and evaluation. To perform RFA, an electrode was inserted targeting the tumor and a virtual 5-mm ablative margin overlaid on the US image. Following ablation, contrast-enhanced US (CEUS) was performed to assess the ablative margin, and the minimal ablative margins were categorized into three groups: (I) margin <0 mm (protrusion), (II) margin 0 to <5 mm, and (III) margin ≥5 mm. Margin assessment was based on the positional relationship between the overlaid tumor plus margin and the perfusion defect of the ablation zone. Tumors in group I underwent repeat ablation until they were in groups II or III. The final classifications were compared with those obtained by retrospectively created fusion images of pre- and post-RFA CT or MR imaging (CT-CT/MR-MR fusion imaging). Results: Treatment evaluation was impossible using CEUS in six HCCs because the tumors were located far below the body surface. Of the remaining 79 HCCs, the categorizations of minimal ablative margins between CEUS extracted-overlay fusion imaging and CT-CT/MR-MR fusion imaging were in agreement for 72 tumors (91.1%) (Cohen's quadratic-weighted kappa coefficient 0.66, good agreement, p<0.01). Conclusions: Extracted-overlay fusion imaging combined with CEUS is feasible for the evaluation of RFA and enables intraoperative treatment evaluation without the need to perform contrast-enhanced CT.